This is in preparation for coq/coq#9274.

This lemma allows one to get the witness out of a later, without having
to use `later_car`, i.e. in a way that works in the on-paper version of
the logic.

Adding a hint without a database now triggers a deprecation warning in
Coq master (https://github.com/coq/coq/pull/8987).

Added a new lemma to allocate fragmented ownership in unital gmaps while updating the full ownership

These results turned out to be neither that useful nor canonical, and can easily
be derived from local updates.

This reverts commit 465dd9f4.

Thanks to @jung for proposing these names.

`sed -i 's/frag_auth_op/frac_auth_frag_op/g' $(find -name "*.v")`